Axial flow blower

ABSTRACT

TECHNICAL PROBLEM 
     To provides a blower which aims at both a noise reduction effect and the inherent blowing performance 
     SOLUTION TO PROGRAM 
     An axial flow blower which is provided with an electric motor, and a blower fan which has a hub which is attached to said electric motor and a plurality of blades which are provided at said hub in a radial manner, wherein in said axial flow blower, a negative pressure surface of a leading edge of each said blade, comprised of a negative pressure surface and a positive pressure surface, is provided with a plurality of triangle shape projections which have vertexes along the leading edge, and the positive pressure surface of the leading edge of each said blade is not provided with said triangle shape projections but is a smooth continuous surface.

TECHNICAL FIELD

The present invention relates to an axial flow blower, more particularly relates to a structure of a fan blade which achieves both noise reduction and blowing performance.

DESCRIPTION OF THE RELATED ART

An axial flow blower is required to provide both blowing performance and low noise. PTL1 discloses to provide a plurality of triangle shape projections in a sawtooth manner (below, referred to as “serrations”) in a chord line direction of a leading edge of a blade as a whole to try to reduce the noise of operation of the blower fan 1. The positive pressure surface and the negative pressure surface of a blade of the axial flow blower become as shown in FIGS. 1A to 10. The serrations of the related art of PTL1 are formed so as to run from the negative pressure surface to the positive pressure surface. For this reason, while the noise reduction effect which serrations create is large, since the serrations are present at the positive pressure surface side, they constitute minus factors in maintaining the lift. Sometimes, the inherent blowing performance of the case with no serrations cannot be obtained.

CITATION LIST Patent Literature

PTL1: Japanese Unexamined Patent Publication No. 2000-087898A

SUMMARY OF INVENTION Technical Problem

The present invention, in view of the above problems, provides a blower which aims at both a noise reduction effect and the inherent blowing performance of a blade by the provision of a plurality of triangle shape projections in the chord line direction of a leading edge part of the blade as a whole at just the negative pressure surface.

Solution to Problem

To solve the above problem, the aspect of the invention of claim 1 provides an axial flow blower (10) which is provided with an electric motor (300), and a blower fan (1) which has a hub (4) which is attached to said electric motor (300), and a plurality of blades (3) which are provided at said hub (4) in a radial manner, wherein in said axial flow blower, a negative pressure surface of a leading edge (6) of each said blade (3), comprised of a negative pressure surface and a positive pressure surface, is provided with a plurality of triangle shape projections which have vertexes along the leading edge (6), and the positive pressure surface of the leading edge (6) of each said blade (3) is not provided with said triangle shape projections but is a smooth continuous surface.

To solve the above problem, the aspect of the invention of claim 7 provides an axial flow blower (10) which is provided with an electric motor (300) and a blower fan (1) which has a hub (4) which is attached to said electric motor (300) and a plurality of blades (3) which are provided at said hub (4) in a radial manner, wherein in said axial flow blower, a leading edge (6) of each said blade (3), comprised of a negative pressure surface and a positive pressure surface, is provided in the negative pressure surface and the positive pressure surface with a plurality of triangle shape projections which have vertexes along the leading edge (6), and angles (φ2) formed by valleys (3-2) of said plurality of triangle shape projections at said positive pressure surface are respectively larger than angles (φ1) formed by said valleys at said negative pressure surface.

Note that the reference numerals given above are illustrations showing the correspondence with specific means described in the embodiments described later.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is an explanatory view for explaining a general axial flow blower.

FIG. 1B is a cross-sectional view along the line A-A of FIG. 1A.

FIG. 1C is an explanatory view for explaining, a positive pressure surface and a negative pressure surface of a blade of FIG. 1B etc.

FIG. 2 is a front schematic view of a first embodiment of the present invention.

FIG. 3 is an example of the results of simulation which analyzes the structure of flow around leading edge serrations.

FIG. 4 is an explanatory view of the results of simulation of FIG. 3.

FIG. 5 is a cross-sectional view of a blade of the simulation of FIG. 3.

FIG. 6 is a perspective view of a first embodiment of the present invention.

FIG. 7 is an explanatory view of a first embodiment of the present invention.

FIG. 8 is a perspective view of a second embodiment of the present invention.

FIG. 9 is an explanatory view of a sixth embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Below, referring to the figures, embodiments of the present invention will be explained. In the embodiments, parts of the same configuration are assigned the same reference notations and the explanations omitted. Referring to FIG. 2, the blower 10 is comprised of a blower fan 1 arranged inside of a shroud 200. It is a so-called electric blower which is driven to rotate by an electric motor 300. The blower 10 is fastened to the engine side of an automobile radiator by mounting parts 250 which are provided near the four corners of the shroud 200 and blows cooling use air to a core part of the radiator. The outer shape of the shroud 200 is a rectangular shape corresponding to a core part of a radiator. At its substantial center, a ring shaped shroud ring part 210 which encompasses the blower fan 1 by its outer circumference is formed. This shroud ring part 210 is provided at the shroud 200 so as to be positioned at the outside of the ring 2 of the blower fan 1 in the radial direction. In the present embodiment, the ring 2 of the blower fan 1 may also be omitted. The blower 10 and later explained blades 3 of the present invention are not limited to automobile radiator use and may also be applied for general industrial use.

Between the shroud ring part 210 and the rectangular shape outer circumference of the shroud 200, an air guide part 220 which expands toward the upstream side of the blower fan 1 is formed. At the center of the shroud ring part 210, a circular motor holding part 230 is formed. This motor holding part 230 is supported by a plurality of motor stays 240 which extend in a radial shape outward in the radial direction and are connected to the shroud ring part 210. At the motor holding part 230, an electric motor 300 is fastened. The shaft of the electric motor 300 and the hub 4 of the blower fan 1 (see FIG. 7) are fastened together. The blower 10 is configured by these blower fan 1, electric motor 300, etc. The hub 4 of the blower fan 1 is tubular in shape and is provided with a plurality of blades 3 in a radial manner. The chord line C, positive pressure surface, negative pressure surface, angle of attack a, lift, etc. of a blade 3 are the same as the general definitions such as shown in FIGS. LA to 1C.

First, at the start, the effects of serrations which form the basis of the present invention will be explained. The simulation of FIG. 3 is for the case of the blade cross-section of FIG. 5 (blade cross-section of the present invention explained later). FIG. 3 is a view of the leading edge seen from the top position. The arrow marks (tangential velocity) which are shown in FIG. 3 are projections of the speed vectors of the flows around the serrations on the projection plane (S plane of FIG. 4) vertical to the Y-Z plane. It will be seen that flows are formed so as to circle in toward the top surfaces of the peaks from the valleys at the two sides. At the serrations, first, small swirls occur at the tips of the peaks. These grow to large swirls the further toward the valleys. Further, behind the peaks, downward flows are formed. Due to this, it is believed that the flow separation which particularly easily occurs at the fast flow rate negative pressure surface is pushed downward to the surface and flow separation is reduced. Due to this, it is possible to ease the disturbances near the blade surfaces and suppress pressure fluctuations at the blade surfaces so as to create an effect leading to noise reduction.

First Embodiment

In the present embodiment, the effects of the above-mentioned serrations are utilized while reducing the rotating noise of the blower fan. The inherent objective of a blower fan, that is, the blowing performance, is kept from being impaired so as to realize both noise reduction and blowing performance (lift). As shown in FIGS. 6 and 7, in the present embodiment, the triangle shapes (serrations) which are provided at the leading edges are provided at only the negative pressure surfaces. The positive pressure surfaces are made the usual blade bottom surfaces, as shown in the cross-sectional view along the line B-B of FIG. 7, so as to maintain the inherent blowing performance (lift). That is, the negative pressure surface of the leading edge 6 of each blade 3, comprised of a negative pressure surface and the positive pressure surface, is provided with a plurality of triangle shape projections which have vertexes along the leading edge 6. On the other hand, the positive pressure surface of the leading edge 6 of the blade 3 is not provided with triangle shape projections, but forms a smooth continuous surface. The triangle shape projections have first slanted sides 3 a, which are slanted with respect to the flow direction of the air flow, and second slanted sides 3 b, which are slanted with respect to the flow direction of the air flow, in a different direction from the first slanted sides 3 a. The triangle shape projections are formed continuously.

As the effect created by the serrations, flow separation is reduced near the blade surfaces of the negative pressure surfaces and disturbances near the blade surfaces are eased. Further, by keeping down pressure fluctuations at the blade surfaces, noise reduction is realized. The present embodiment not only can achieve both noise reduction and blowing performance (lift), but also can perform blowing work more efficiently than even conventional blower fans, so lower torque is realized and the power used becomes smaller, so this leads to energy saving.

Second Embodiment

The second embodiment is characterized as follows. The side surfaces 3-3 of the peaks 3-1 of the triangle shape projections are slanted like the slopes of mountains. The side surfaces 3-3 of the peaks 3-1, as shown in FIG. 8, are slanted, so that the angles φ2′ formed by the valleys at the bottom surfaces 3-4 of the valleys between one peak 3-1 and another peak 3-1 becomes greater than the angle φ1 formed by the valleys at the negative pressure surface. The slanted surfaces may be flat or may be curved. They may be provided at both side surfaces 3-3 of the peaks 3-1 or at single sides. The angles φ1 and φ2′ formed by the valleys are made angles at the planes vertical to the axial center of the blower fan (same for later explained (φ2). In the present embodiment, at the serrations, smooth swirls are formed. These grow into larger swirls the further toward the valleys. Further, at the rear of the peaks, downward flows are formed. These push the flow separation downward and can reduce the flow separation.

Third Embodiment

The sizes “a” of the bottom sides of the peaks 3-1, the angles ψ of the vertexes, and the center directions “O” of the triangle shape projections (see FIG. 8) are changed as the projections become closer to the outer circumference or ring 2 of the blower fan 1. In the blower fan 1, sometimes distinctive, flows are formed in the flow of air flow in the radial direction. If dealing with the flows by suitably changing the sizes “a” of the bottom sides of the peaks 3-1, the angles ψ of the vertexes, and, the center directions O, it is possible to reduce the flow separation even more. As these distinctive flows, diagonal flows, or, back flows from the outer circumference or ring 2 of the blower fan 1 etc. may be mentioned. In the present embodiment, the peaks 3-1 of the triangle shape projections are modified for these flows (turning center direction “O” in direction of air flow etc.) Due to this, it is possible to control the flows so as to minimize the noise which is generated due to the disturbance of the air flow.

Further, in the case of an axial flow blower, the further to the outer circumference side of the blower fan 1, the faster the flow rate is. Sometimes it is effective to increase the size “a” of the bottom side or reduce the angle ψ of the vertex the further to the outer diameter side of the blades. It is possible to control the fast flow rate flow where separation easily occurs, by changing the shapes of the peaks 3-1 of the triangle shape projections.

Fourth Embodiment

The fourth embodiment, while not shown, provides serrations which run through the blade thickness at the trailing edge 7 of the blade 3. This is an embodiment where, in the embodiments explained above, the negative pressure surface to the positive pressure surface of the trailing edge 7 of the blade 3 is provided with a plurality of triangle shape projections along the trailing edge 7. In addition to the effects of the embodiments explained up to here, the disturbances in the back flow of the blades can be reduced, so it is possible to obtain the effects of noise reduction, reduction of the air flow, and prevention of the increase of the drive torque.

Fifth Embodiment

The fifth embodiment is an embodiment in the case of applying the embodiments which were explained above to a shape of blade such as shown in FIG. 7, where the end at the outer circumferential side is swept back from the direction of rotation, that is, a backward curved blade (sweptback blade). Of course, the invention may also be applied to a shape of blade where the end at the outer circumferential side is swept forward from the direction of rotation, that is, a forward curved blade (forward swept blade).

Sixth Embodiment

In the sixth embodiment, the leading edge 6 of blade 3 in the negative pressure surface and the positive pressure surface 3 is provided with a plurality of triangle shape projections which have vertexes along the leading edge 6.

In this embodiment, the angles φ2 which are formed by the valleys 3-2 of the plurality of triangle shape projections at the positive pressure surface are all larger than the angles φ1 which are formed by the valleys of the negative pressure surface. In this case as well, the positive pressure surface can maintain the blowing performance (lift), compared with negative pressure surface. When the angles φ2=180 degrees, the result becomes included in the second embodiment. Further, when the angles φ2 are close to 180 degrees, it is possible to obtain substantially the same effects as the second embodiment. Of course, if the angles φ2 are larger than the angles φ1, the positive pressure surface can maintain the blowing performance (lift) compared with negative pressure surface.

EXPLANATION OF REFERENCE NUMBER

-   1 blower fan -   3 blade -   4 hub -   300 electric motor 

1. An axial flow blower which is provided with an electric motor, and a blower fan which has a hub which is attached to said electric motor, and a plurality of blades which are provided at said hub in a radial manner, wherein in said axial flow blower, a negative pressure surface of a leading edge of each of said blades, comprised of a negative pressure surface and a positive pressure surface, is provided with a plurality of triangle shape projections which have vertexes along the leading edge, and the positive pressure surface of the leading edge of each of said blades is not provided with said triangle shape projections but is a smooth continuous surface.
 2. The axial flow blower as set forth in claim 1, wherein said triangle shape projections have peaks with slanted side faces.
 3. The axial flow blower as set forth in claim 1, wherein said triangle shape projections have peaks with bottom sides which are changed in size as said triangle shape projections closer to an outer circumference of said blower fan.
 4. The axial flow blower as set forth in claim 1, wherein said triangle shape projections have peaks with vertexes which are changed in angle as said triangle shape projections closer to an outer circumference of said blower fan.
 5. The axial flow blower as set forth in claim 1, wherein said triangle shape projections have peaks with center directions which are changed as said triangle shape projections closer to an outer circumference of said blower fan.
 6. The axial flow blower as set forth in claim 1, wherein a blade trailing edge of each said blades is provided in the negative pressure surface and the positive pressure surface with a plurality of triangle shape projections which have vertexes at the blade trailing edge.
 7. The axial flow blower which is provided with an electric motor and a blower fan which has a hub which is attached to said electric motor and a plurality of blades which are provided at said hub in a radial manner, wherein in said axial flow blower, a leading edge of each said blade blades, comprised of a negative pressure surface and a positive pressure surface, is provided in the negative pressure surface and the positive pressure surface with a plurality of triangle shape projections which have vertexes along the leading edge, and angles formed by valleys of said plurality of triangle shape projections at said positive pressure surface are respectively larger than angles formed by said valleys at said negative pressure surface.
 8. The axial flow blower as set forth in claim 1, wherein said blower fan has backward curved blades or forward curved blades.
 9. A blower fan which is provided with a hub which is attached to a drive device and a plurality of blades which are provided at said hub and have a negative pressure surface and a positive pressure surface, wherein in said blower fan, a negative pressure surface of a leading edge of each said blade has a first slanted side, which is slanted with respect to the flow direction of the air flow, and a second slanted side, which is slanted with respect to the flow direction of the air flow, in a different direction from said first slanted side and is provided with a plurality of projections which project out into the upstream side of flow of the air flow, and said positive pressure surface of a leading edge of each said blade is not provided with said triangle shape projections but is a smooth continuous surface. 